Add continuous hardware health monitoring and component detail view

- kmsg watcher now records kernel errors (GPU Xid, MCE, EDAC, storage I/O) at all times,
  not only during SAT tasks; flushImmediate writes directly to ComponentStatusDB
- New health_poller: polls ipmitool sdr every 60s for PSU health (watchdog:psu source)
- Hardware Summary card auto-refreshes every 30s via htmx without page reload
- Component rows (CPU/Memory/Storage/GPU/PSU) are now clickable -- opens a modal
  with per-component status, source, timestamp and last 20 history entries

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

audit/internal/webui/server.go

@@ -221,6 +221,11 @@ func NewHandler(opts HandlerOptions) http.Handler {
 		h.kmsg = newKmsgWatcher(opts.App.StatusDB)
 		h.kmsg.start()
 		globalQueue.kmsgWatcher = h.kmsg
+
+		// Start periodic health poller for components that don't emit kernel log events (e.g. PSU).
+		if opts.App.StatusDB != nil {
+			newHealthPoller(opts.App.StatusDB).start()
+		}
 	}
 
 	globalQueue.startWorker(&opts)
@@ -328,6 +333,10 @@ func NewHandler(opts HandlerOptions) http.Handler {
 	mux.HandleFunc("GET /api/install/disks", h.handleAPIInstallDisks)
 	mux.HandleFunc("POST /api/install/run", h.handleAPIInstallRun)
 
+	// Hardware component detail (fragment for modal in Hardware Summary card)
+	mux.HandleFunc("GET /api/hardware-summary", h.handleAPIHardwareSummary)
+	mux.HandleFunc("GET /api/components/{type}", h.handleAPIComponentDetail)
+
 	// Metrics — SSE stream of live sensor data + server-side SVG charts + CSV export
 	mux.HandleFunc("GET /api/metrics/stream", h.handleAPIMetricsStream)
 	mux.HandleFunc("GET /api/metrics/latest", h.handleAPIMetricsLatest)